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Optimized temporal binning of comparison star measurements for differential photometry

Hartley, Kathryn E; Wilson, R W

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Kathryn Hartley
Post Doctoral Research Associate


Ground-based, high precision observations of the light curves of objects such as transiting exoplanets rely on the application of differential photometry. The flux of the target object is measured relative to a comparison star in the same field, allowing correction for systematic trends in the light curve, mainly due to atmospheric effects including the variation of extinction with airmass. However, the precision of the light curve is then limited by the random noise for the measurements of both the target object and the comparison star. For time-resolved photometry using short exposure times of up to a few tens of seconds, the time-scale of the systematic variations due to atmospheric (or other) effects can be much longer than the cadence of the observations. In this case, the overall signal-to-noise ratio of the observation may be improved significantly by applying some temporal binning to the measurements of the comparison star, before comparison with the target object, without reducing the cadence of the overall light curve. In this paper, we will describe a data reduction pipeline for implementing this method which optimizes the number of frames to be binned for the comparison star, and we present example results for time-resolved photometric data. An example of applying the technique on an exoplanet transit light curve of WASP-166b is presented using four comparison stars of different magnitudes.


Hartley, K. E., & Wilson, R. W. (2023). Optimized temporal binning of comparison star measurements for differential photometry. Monthly Notices of the Royal Astronomical Society, 526(3), 3482-3494.

Journal Article Type Article
Acceptance Date Sep 25, 2023
Online Publication Date Sep 28, 2023
Publication Date 2023-12
Deposit Date Nov 8, 2023
Publicly Available Date Nov 8, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 526
Issue 3
Pages 3482-3494
Keywords Space and Planetary Science; Astronomy and Astrophysics
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Copyright Statement
© 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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